1. Field of the Invention
The present invention provides a decoding apparatus and method thereof, and more particularly, the present invention provides a quadrature amplitude modulation trellis coded modulation (QAM-TCM) apparatus and related decoding method thereof.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 illustrates a functional block diagram of a 64 quadrature amplitude modulation trellis coded modulation (QAM-TCM) encoding apparatus 10. The QAM-TCM encoding apparatus 10 includes a parser 20, a differential encoder 22, a convolutional encoder 24, a puncturing unit 26, and a QAM mapper 28. Firstly, after the parser 20 receives four symbols RS1, RS2, RS3, RS4 sequentially, the parser 20 rearranges and then outputs the bits of the symbols RS1, RS2, RS3, RS4. For example, assume that the symbols RS1 includes seven bits, which are: I1, I2, I4, I5, I7, I8, I10; the symbol RS2 includes seven bits, which are: I11, I12, I13, I0, I3, I6, I9; the symbol RS3 includes the seven bits, which are: Q1, Q2, Q4, Q5, Q7, Q8, Q10; and the symbol RS4 includes the seven bits, which are: Q11, Q12, Q13, Q0, Q3, Q6, Q9. After the parser 20 receives the symbols RS1, RS2, RS3, RS4, the parser 20 outputs two sets of in-phase bits I2, I5, I8, I11, I13 and I1, I4, I7, I10, I12, two sets of quadrature-phase bits Q2, Q5, Q8, Q11, Q13 and Q1, Q4, Q7, Q10, Q12, four in-phase bits I0, I3, I6, I9, and four quadrature-phase bits Q0, Q3, Q6, Q9. Next, the differential encoder 22 executes encoding on the four in-phase bits I0, I3, I6, I9 and the four quadrature-phase bits Q0, Q3, Q6, Q9 to generate a set of in-phase and a set of quadrature-phase bits I′ and Q′ respectively as shown in FIG. 1. Please continue to refer to FIG. 1. The convolutional encoder 24 then encodes the set of in-phase and the set of quadrature-phase bits I′ and Q′ respectively to further generate a set of in-phase and a set of quadrature-phase bits I″ and Q″ respectively. Please note that since the convolutional encoder 24 executes encoding with a 1/2 ratio, the number of bits of the set of in-phase bits I″ or that of the set of quadrature-phase bits Q″ is twice the number of the set of in-phase bits I′ or that of the set of quadrature-phase bits Q′. In other words, this means that each of I″ and Q″ has 8 bits. Please continue to refer to FIG. 1. Next, the puncturing unit 26 punctures, or removes, three bits from each set of in-phase and quadrature-phase bits I″ and Q″ to generate a set of in-phase encoded bits Iec and a set of quadrature-phase encoded bits Qec. Please note that each of these sets has 5 bits. Lastly, the QAM mapper 28 executes a mapping procedure by inputting two sets of in-phase bits, which are: I2, I5, I8, I11, I13 and I1, I4, I7, I10, I12, two sets of quadrature-phase bits, which are: Q2, Q5, Q8, Q11, Q13 and Q1, Q4, Q7, Q10, Q12, and finally the set of in-phase encoded bits Iec and the set of quadrature-phase encoded bits Qec to generate an in-phase bit flow X and a quadrature-phase bit flow Y. For example, the QAM mapper 28 first executes the mapping procedure on a sequence of input bits I1, I2, Iec1 and a sequence of input bits Q1, Q2, Qec1 to generate a set of in-phase bits X1 and a set of quadrature-phase bits Y1. Next, the QAM mapper 28 executes the mapping procedure on a sequence of input bits I4, I5, Iec2 and a sequence of input bits Q4, Q5, Qec2 to generate a set of in-phase bits X2 and a set of quadrature-phase bits Y2. Hence, each set of in-phase bits: X1, . . . , Xn forms the above mentioned in-phase bit flow X, and each set of the quadrature-phase bits: Y1, . . . , Yn forms the above mentioned quadrature-phase bit flow Y. As was mentioned previously, the QAM-TCM decoding technology is well known to those possessing average skilled in the pertinent art. Additionally, for reference regarding this topic one may also refer to the detailed descriptions in articles such as, “Digital Multi-Programme Systems for Television, Sound and Data Services for Cable Distribution”, ITU-T Recommendation J.83, whose contents are incorporated herein by reference in its entirety. Therefore, given the wealth of prior art knowledge not further reiteration is necessary herein.
Furthermore, it is to be noted that U.S. Pat. No. 6,233,712 discloses a QAM-TCM decoding apparatus, the apparatus executes depuncturing, Viterbi decoding procedures on all bits of the in-phase, quadrature-phase bit flow X, Y received directly through a transmission channel. This decoding process leads to a significant amount of calculation, and hence increases the computational complexity of the decoding calculation.